This invention relates to electromagnetic energy, and more particularly, to providing more efficient electromagnetic exposure.
U.S. Pat. No. 5,998,774, which is incorporated by reference in its entirety, describes an invention for creating uniformity over a cylindrical region, herein referred to as the standard cylindrical reactor. Unfortunately, the exposure width of this invention for maintaining true uniformity is limited by the maximum waveguide width for keeping the electromagnetic wave in TE10 mode. Limited width has a disadvantage in exposing materials that require a longer exposure time to microwave energy. Similarly, some materials are not able to withstand a high power density, and a wider exposure region would lead to a lower power density.
An elliptical exposure chamber has an extended focal region. In an exemplary embodiment, a plurality of cylindrical reactors form the extended focal region. Reducing the size of the opening to each cylindrical reactor reduces the amount of energy reflected and increases the overall heating. In order to efficiently deliver the electromagnetic energy to the reduced opening, a tapered waveguide has a concave end. A power splitter divides power from a central waveguide to the plurality of cylindrical reactors. The power that is delivered to each cylindrical reactor can be adjusted by adjusting the impedance of each reactor (i.e. increasing or decreasing the impedance matching), adjusting the width of each reactor, or adjusting the width of the opening to each reactor. The width of the opening to each reactor can be controlled by, for example, a movable metal plate. A dielectric wheel can be used to shift hot spots along the focal region.